A multiple-input multiple-output (MIMO) technology increases a data rate and reliability of a radio communication system by installing a plurality of antennas in a transmitting terminal and a receiving terminal. However, studies on almost all of the MIMO technologies in the related art have a limitation in that an influence due to interference between adjacent cells in a multi-cell environment as an actual radio communication environment is not considered, because only a single cell environment is considered.
In a radio communication system that is based on a multi-cell environment, it is very important to resolve the problem, such as interference between adjacent cells. In particular, since an influence due to interference between the cells increases while a frequency reutilization rate between cells increases, the interference is the main cause for obstruction such that a high-speed radio data rate cannot be achieved. The MIMO technology has attracted attention as a means for resolving the problem such as interference between the cells, but studies that actively use multiple antennas to solve the problem are at an initial stage.
Conventional studies that are related to a MIMO technology in a multi-cell environment are as follow. Kang Ji-Woong, Je Hi-won, and Lee Kwang-Bok suggested a transmit antenna selection method in consideration of interference between adjacent cells in a multi-cell environment (J. W. Kang, H. W. Je, and K. B. Lee, “Transmit Antennas Subset Selection for Downlink MIMO Systems”, in Proc. IEEE International Conference on Communications 2007 (ICC2007), June 2007)). Blum proved that an optimal transmission method using multiple antennas is dependent on the type of an influence due to interference between adjacent cells, on the assumption that a transmitting terminal does not know channel information (R. S. Blum, “MIMO Capacity with Interference”, IEEE Journal on Selected Areas in Communications. Vol. 21, no. 5, pp. 793 to 801, June 2003). Ye suggested a technology that determines a transmission method of multiple antennas in consideration of an influence due to interference between adjacent cells in a multi-cell environment (S. Ye, and R. S. Blum, “Optimized Signaling for MIMO Interference Systems with Feedback”, IEEE Transactions on Signal Processing, vol. 51, no. 11, pp. 2848 to 2939, November 2003). However, in order to use the technology that was suggested by Ye, each of the transmitting terminals should know the channel statuses of all links on a system including the transmission methods that are used by transmitting terminals in other cells. Therefore, it is difficult for this technology to be actually applied to the system. In brief, the conventional studies that are related to the MIMO technologies in the multi-cell environment are still at an initial stage, and in particular, studies that are related to a multi-user disclosed in the present invention is insufficient.